The fledgling Symphony Silicon Valley declared its just-completed third season a success this week, with a balanced budget and a newly created endowment to show for its efforts. “Symphony Silicon Valley formed after the collapse of the 123-year-old San Jose Symphony in 2001. The new symphony has started slowly — 17 performances last year compared with 50 a year for the old symphony — and has survived mostly without city or corporate funding, depending on private donors and ticket sales.” The new endowment will pump $50,000 a year into the budget, and adinistrators hope it will encourage private support for the ensemble.